import heapq
def dijkstra(s):
    hq=[]
    heapq.heappush(hq,[0,s])
    dist=[-1 for _ in range(N)]
    karidist=[10**9+1 for _ in range(N)]
    while len(hq)!=0:
        d,p=heapq.heappop(hq)
        if dist[p]==-1:
            dist[p]=d
            for e,c in edge[p]:
                if karidist[e]>d+c:
                    karidist[e]=d+c
                    heapq.heappush(hq,[d+c,e])
    return dist

def csv(i,j):
    return i*W+j

import sys
input=sys.stdin.readline
H,W,N=map(int,input().split())
dat=[]
poses=[(0,0),(H-1,W-1)]
poses=set(poses)
for i in range(N):
    a,b,c,d=map(int,input().split())
    a-=1
    b-=1
    c-=1
    d-=1
    dat.append([a,b,c,d])
    poses.add((a,b))
    poses.add((c,d))
edge=[[] for _ in range(len(poses))]
poses=list(poses)
from collections import defaultdict
dic=defaultdict(lambda:-1)
for i in range(len(poses)):
    dic[poses[i]]=i
for a,b,c,d in dat:
    edge[dic[(a,b)]].append([dic[(c,d)],1])
for i in range(len(poses)):
    for j in range(i+1,len(poses)):
        a,b=poses[i]
        c,d=poses[j]
        edge[i].append([j,abs(a-c)+abs(b-d)])
        edge[j].append([i,abs(a-c)+abs(b-d)])
N=len(poses)
dist=dijkstra(poses.index((0,0)))
print(dist[poses.index((H-1,W-1))])